Monday, 11:50 a.m.
A few records have already been broken this morning, including the 16 below reading at Chicago's O'Hare Airport. That bested the old mark by two degrees, and when combined with the winds sustained at 15 to 25 mph with gusts to 30 mph, made it feel as if it was 40 below! There have been very few days in the past 20 years with temperatures that far below normal, and having a day stay this far below zero. Feb. 2-4 1996, stands out in that regard, when temperatures stayed below zero for the better part of three days.
If you look at the 1000-500 mb thicknesses, the lowest values are over them right now:
That thermal trough extends right down to the western Gulf Coast, with areas to the west out in the Plains, though extremely cold, actually undergoing some sort of warm advection. Look at the temperatures aloft:
This is one of those air masses where the difference from one side of the cold front to the other is dramatic, and it is one of those air masses where temperatures will go down regardless of the time of day as the arctic air drills in, and go up as the core of the coldest air starts moving downstream. Look at the 24-hour temperature change from 10 a.m. yesterday to 10 a.m. today:
The stubborn low-level cold air that was tough to rout out of the interior mid-Atlantic and New England yesterday has, by and large, given way to a dramatically warmer air mass, with temperatures in the 50s to near 60 right now across all of southern New England. In contrast, once the front passes, some of the temperature changes since this time yesterday have been well over 40 degrees! I suspect those 24-hour changes, when looked at tomorrow morning, will be even larger in parts of the mid-Atlantic and New England, perhaps over 50 degrees!
Records are likely to tumble tonight all the way to the Gulf Coast, and a few may disappear in the East as well as this polar vortex rotates across the Lakes into Quebec:
As bitter as it is, the atmosphere will look a lot different by the end of the week. Look at the projected 850 mb temperatures for Friday evening:
Much as we saw with temperatures in the East this past weekend, the low-level arctic air won't be chased away easily, but the air aloft will moderate rather easily after tomorrow. Then it will be a matter of time before mixing takes that warmth aloft and brings some of it down to the surface. Before we get there, however, a 48-hour period of intense cold is in store for most of the country from the Plains to the East Coast.
Heavy rain will soak drought-stricken areas of the mid-Atlantic over the next couple of days. Focus will then shift to Matthew and its potential to impact the Eastern Seaboard with more heavy rain later next week.
Summer has ended astronomically, but from a meteorological standpoint, there's plenty more warm weather heading into October from the Plains to the East.
Two strong cold fronts will charge across the country in the next week, eventually taking out the current hot and humid air mass from the Plains to the East Coast.
Over the next three days, hot and humid air will expand across the Mississippi Valley all the way to the East Coast. This will be followed by even more heat and humidity leading into the weekend.
Hermine will head across the Florida Panhandle late tonight, then cut across the coastal Carolinas and become a headache for the mid-Atlantic and southern New England over the Labor Day weekend. It will be followed by a heat wave later next week.
The heat and humidity will be erased from much of the East later this week, but warmth will spread from the Plains eastward over the weekend. The tropics could still play an important role in the weather along the Eastern Seaboard this weekend.